Cyclic durable high-capacity Sn/Cu6Sn5 composite thin film anodes for lithium ion batteries prepared by electron-beam evaporation deposition

Sn/Cu6Sn5 alloy composite thin films were directly prepared by electron-beam deposition for anodes of lithium ion batteries. The thin film was comprised of micro/sub-microcrystalline Sn and Cu6Sn5, where the polyhedral micro-sized Sn grains were uniformly dispersed in the loose Cu6Sn5 matrix. Lithiation reaction kinetics were confirmed to be controlled by a diffusion step and the diffusion coefficient of Li+ in the thin film anode was determined to be 1.91 × 10−7 cm2/s. The galvanostatic cycling behavior of Sn/Cu6Sn5 composite thin film anodes was studied under different conditions. Stable capacities of more than 370 mAh/g were obtained by discharging from 1.25 to 0.1 V. Structure changes and fading mechanism of the thin film electrodes was discussed based on SEM, XRD and EDX investigations. The present results demonstrated that the multi-phase composite structure can improve electrochemical performance of the Cu–Sn alloy thin film electrodes.